President Obama put forward a plan last week to make access to high-quality early learning a reality for every 4-year-old in America by making full-day preschool available to families with incomes at or below 200 percent of the federal poverty line.

Parents, teachers and principals nationwide agree that we need to do more to ensure that children from disadvantaged families begin kindergarten at the same educational starting line as do children from better-off families. The president’s plan includes a cost-sharing arrangement with states, with the entire federal investment of $75 billion covered by a new cigarette tax, and with incentives for states to make programs available for even more middle-class families.

Members of Congress have asked me: How do we know early learning works? What about its lasting impact?

Let’s examine the record.

At an elementary school I recently visited in Bladensburg, teachers told me how much better-prepared students are for the classroom if they’ve been to preschool. “It makes a huge difference,” said one 21-year teacher.

Research backs her up. Studies consistently demonstrate that high-quality early education gives children the foundation they need to succeed. No study is perfect, but the cumulative evidence that high-quality preschool works is overwhelming. Consider a study of 4-year-olds in Tulsa who attended Oklahoma’s high-quality universal preschool program, with small class sizes and well-trained teachers — features that are components of the president’s proposal. They started kindergarten seven months ahead in literacy skills and four months ahead in math skills. Likewise, children who attended Boston’s high-quality preschool program gained seven months in literacy and math. Studies of preschoolers in New Jersey showed substantial gains in literacy and math. These consistent gains are critical steps toward long-term success in school.

Skeptics of early learning say these programs “don’t work” because some studies have failed to find major effects in later grades — the so-called “fade out.” But that’s not quite right.

The most rigorous research that can be compared with what we are proposing — high-quality, full-day preschool — shows crucial benefits in high school graduation rates, employment and avoidance of criminal behavior. Although the best scientific evidence for the long-term effects of early education comes from studies of multiyear programs dating to the 1960s and 1970s, a recent study of New Jersey students who received one year of high-quality public preschool found that by fifth grade, they were less likely to be held back or placed in special education. The few more recent long-term assessments of public preschool consistently indicate similar benefits, including increased graduation rates and reduced arrest rates.

High-quality preschool appears to propel better outcomes by enhancing non-cognitive skills such as persistence, self-control and emotion regulation — skills that depend on early brain development and social experiences and contribute to long-term academic outcomes and career success.

The study often cited by skeptics — the Head Start Impact Study — isn’t a great comparison to the president’s proposal. It examined the effect of offering access to Head Start, not the effect of participation (nearly 20 percent of the 4-year-olds in the Head Start group never attended). The president’s proposal would require higher qualifications for staff than was the case in this study, and this administration has begun putting in place needed quality-control improvements to Head Start.

Preschool works. But is it worth the cost?

Studies of the savings from high-quality early learning demonstrate that the answer is yes. Graduates of such programs are less likely to commit crimes or rely on food stamps and cash assistance; they have greater lifetime earnings, creating increased tax revenue. Although the range of savings varies across studies, the studies consistently find robust returns to taxpayers.

Can we replicate what works? We can, and we must. If the United States is to remain a global economic leader, high-quality preschool must become the norm. The moral case is compelling, too. As President Obama has said, every child should have the opportunity, through hard work, to join the middle class. Children shouldn’t be denied equal educational opportunity at the starting line.

The countries we compete with economically are well ahead of us in preschool opportunity. We rank 28th in the proportion of 4-year-olds enrolled in early learning in surveys by the Organization for Economic Cooperation and Development, and 25th in public funding for early learning. Fortunately, we have great examples to learn from: Oklahoma, Georgia, New Jersey and Boston all have excellent preschool programs.

Making quality early-learning opportunities a norm for every 4-year-old will take more than money. It will take a new commitment to recruiting and keeping excellent staff, and tackling many of the other challenges in our K-12 system. That’s why we propose to invest an additional $750 million to support innovation and preschool capacity-building in states. To make a critical difference for all children, high-quality early learning must be followed by rich educational opportunities and robust learning experiences at every stage of the journey to college and careers.

The evidence is clear. We need to stop asking whether early learning works — and start asking whether we have the national will to make it a reality for the children who need it most.

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Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.